J. Lalonde et al., PROTEASE STABILIZATION BY HIGHLY CONCENTRATED ANIONIC SURFACTANT MIXTURES, Journal of the American Oil Chemists' Society, 72(1), 1995, pp. 53-59
We have found that anionic surfactants such as linear alkylbenzene sul
fonate (LAS) can solubilize proteases in a substantially nonaqueous en
vironment without loss of proteolytic activity. Moreover, in mixtures
of anionic and nonionic surfactants with a moderate amount of water (w
ater less than 30 wt%), controlled levels of LAS and water solubilize
pro teases; yet, in these concentrated surfactant mixtures, enzymes ma
intain their activity for extended periods. Experimental design techni
ques have been used to delineate the relationship between protease sta
bility and the water, pH and anionic surfactant levels in these surfac
tant concentrates. As the sum of water and LAS levels is increased, ma
ximum enzyme stability is observed, after which stability falls off. A
t low water and LAS levels (sum of both <20%), protease solubility is
low, while at high levels of water and LAS (sum of LAS and water >45%)
, denaturation predominates. Additionally, we have developed a new and
simple method to predict protease stability by which a synthetic pept
ide is used to measure protease activity directly in the surfactant co
ncentrate. From the application or this new technique to our system an
d to commercial liquid detergent formulations, it is apparent that wat
er facilitates the loss of activity of proteases in surfactant concent
rates by increasing the rate of autolysis.